I think you are REALLY discounting the Sansa. Zune is better "quality"? Let's talk about that quality for a sec. The Sansa supports Asian character sets.....Zune? Yeah right. I also noticed the Sansa supports wi-fi now....so much for that feather in Microsoft's hat. Thirdly, you can buy a Sansa in just about any country you want AND be able to put music on it (Canada...oh wait no music store!)
Microsoft has proven to me that Zune is really just a bunch of marketing hacks with no ability to execute on technical vision. You can talk about "social" all you want but its really just a big vision that is unattainable because they lack the programming knowhow to make it happen.